Short communicationUse of solid-phase microextraction to detect and quantify gas-phase dicarbonyls in indoor environments
Introduction
There is a need for new analytical techniques to measure the products of indoor chemistry that are short lived, highly reactive, thermally labile, or highly oxidized—“stealth chemicals” [1]. These “stealth chemicals” can be present in indoor environments when initiator species such as O3 (ozone), for example, react with volatile organics compounds (VOCs) to form oxygenated organic compounds such as aldehydes, ketones, and dicarbonyls. In a recent paper by Jarvis et al., chemicals with carbonyl substructures (especially when the functional group was present twice or more in the same molecule) were associated with the potential to cause work-related asthma [2], [3]. To characterize the indoor environment, industrial hygienists, for example, require analytical techniques that can adequately sample these species. Sampling and detecting the various carbonyl compounds in the indoor environment is an essential step to assessing health impacts [4]. Glyoxal and methylglyoxal are difficult to sample and detect due to their polarity and highly reactive nature. The greater the polarity of a compound; the more arduous it becomes to detect using direct GC analysis. Additionally, polar analytes are not suitable for thermal desorption-GC analysis [4]. In separation sciences, derivatization is used to improve the chromatographic properties and/or the sensitivity of the detection [5] and has other advantages that include: (1) providing analyte specificity based on key functional groups, (2) allowing detection with conventional detectors, and (3) acting as a method for conformation that the compound of interest is present in the sample [6]. An established method for detecting carbonyl compounds is to react them with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA) to form oximes which are then analyzed by GC with MS detection [7], [8], [9], [10], [11], [12]. Solid-phase microextraction (SPME) with on-fiber derivatization supports the feasibility of coupling on-sorbent derivatization and subsequent sampling with thermal desorption anaylsis [4]. Martos and Pawliszyn have demonstrated that the combination of on-fiber derivatization and thermal desorption is a sensitive technique to sample and analyze airborne polar analytes [6]. More recently, gas-phase atmospheric research has effectively demonstrated the use of SPME fibers pre-coated with PFBHA for on-fiber derivatization of carbonyl-containing compounds [8], [13].
SPME is an extraction technology that combines sampling and sample preparation. Since conception, SPME has been widely used for research applications in pharmaceutical, food, fragrance, forensic, environmental and physicochemical areas [14]. Conventional air-sampling methods use sorbent tubes, impingers, vacuum canisters, gravimetric filters, pumps, and light scattering devices [15]. Many of these methods require considerable sampling expertise and costly equipment, lengthy sample collection and preparation periods, and complicated cleaning and extraction procedures [16]. SPME offers many advantages for air sampling and some of these are: high precision and sensitivity, wide range of sampling times, applicability to a wide range of compounds, reusability, possibility of automation, solventless extraction, and compatibility with conventional analytical equipment [14]. The primary objective of this research is to determine the potential for using PFBHA-loaded SPME fibers for detecting and quantifying glyoxal and methylglyoxal in the indoor environment.
Section snippets
Reagents
The following reagents were used as received from Sigma-Aldrich (St. Louis, MO) and had the following purities: methylglyoxal (MGLY) 40% aqueous solution, glyoxal (GLY) 40% aqueous solution, and O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride 98+%. The reagent water was distilled and deionized to resisitivity of 18 MΩ cm, and filtered using a Milli-Q filter system (Billerica, MA). Compressed air from the National Institute for Occupational Safety and Health (NIOSH) facility was passed
PFBHA-fiber saturation optimization
An optimum PFBHA loading time ensured that the maximum amount of PFBHA derivatizing agent could be adsorbed onto the fiber while minimizing the PFBHA exposure time. The saturated level of PFBHA adsorbed on the SPME fiber was necessary to ensure that there was a sufficient amount of PFBHA available to derivatize the sampled dicarbonyls. A 15 min fiber exposure time produced 91% of the maximum PFBHA-fiber loading while keeping the exposure time to a minimum. Therefore, all subsequent PFBHA-fiber
Conclusion
There is great potential for the use of PFBHA-loaded SPME fibers for detecting and quantifying gas-phase dicarbonyls, particularly MGLY, in indoor air environments. The results of this study show that using the PDMS/DVB SPME fiber for on-fiber derivatization and subsequent sampling for MGLY provides a good combination of analytical reproducibility and sensitivity. Linearity of the calibration curve was achieved across a range of 11–222 μg/m3 (4–75 ppb). The results obtained by using the PDMS/DVB
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